This multidisciplinary translational research project has generated a predominantly human sequence monoclonal antibody (mAb) with high affinity (Kd = 4 nM) for cocaine and specificity over cocaine's inactive metabolites. This unique new molecular entity (preclinical designation, 2E2, a human gamma 1 (?1) heavy chain and mouse lamda (?) light chain) is at an advanced stage of preclinical development for use in the prevention of relapse in treatment-seeking cocaine abusers. The development of 2E2 has met several key safety and efficacy milestones. The mostly human structure of this mAb should be safe for repeated treatments in patients and should confer long-term efficacy. Anti-cocaine mAbs bind to and sequester cocaine in the peripheral circulation and we have shown that 2E2 dramatically lowers brain cocaine concentrations in mice. Furthermore, 2E2 decreases the effect of cocaine in a rat model of relapse. Our industry collaborator, Vybion Inc., has reengineered a novel version of our mAb with a human kappa (?) light chain constant region replacing the mouse constant region. The reengineered mAb protein (h2E2) has been transiently expressed and h2E2 retains the identical affinity and specificity for cocaine as 2E2. This represents a proof-of-concept milestone and h2E2 represents our new lead candidate for commercialization. Work will be continued towards the development of a stably transfected mammalian cell line capable of the high level production of h2E2, which will be required for its clinical development. Targeted modifications of h2E2's primary structure aim to increase protein expression levels and stability, thereby enhancing the cost-effectiveness of production. The overall goal of the proposed studies is to provide the comprehensive structural and efficacy data for the highly expressed variant of h2E2 and then produce sufficient quantities of purified h2E2 to support the in vivo toxicology studies that are required for an IND application to the FDA.